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no compression - 3/3/2004 9:01:42 PM   
Dr.Weasel



Posts: 184
Joined: 2/15/2004
From: layton, UT, USA
Status: offline 		(Look at post number four below)

One my Cox sure start .049 i'm getting no compression and it leaks fuel. I have inspected the treads on the plug and the cylinder and they are fine. I have also torque the plug down and still nothing. I there some gap filler or something i can use to seal the head?

Thanks
The Doc.

P.S. Dont buy Cox they suck big time!!!!

< Message edited by Dr.Weasel -- 3/4/2004 10:04:07 PM >
       Post #: 1

RE: no compression - 3/3/2004 9:51:15 PM   
DesignMan



Posts: 269
Joined: 10/11/2002
From: Cerritos, CA, USA
Status: offline 		You should have a minimum of one copper gasket between the head and cylinder. Also, where is the leakage? Sometimes plugs have blown center-post seals.

One other thing can happen, and that is where the gasket goes in a little off-center, ends up in the threads, and holds up the tightening of the plug. Pull the head, remove the gasket and examine it to be sure it is perfectly flat.

(in reply to Dr.Weasel)
       Post #: 2

RE: no compression - 3/3/2004 11:26:51 PM   
ajcoholic



Posts: 4045
Joined: 6/22/2002
From: Kirkland Lake, ON, CANADA
Status: offline 		Was it a sudden occurance? Or like that from new? Was it running fine and then lost compression or was it after a glow head change? Things just dont "happen" on their own, something had to happen. More info and we could probably help you better

I assume you are running this in a control line plane - when you plant the airplane (if you do) and get a bit of dirt in the exhausts, do you clean it out with fuel and make sure not to turn over the engine with even a wee bit of dirt there? I wore out too many piston/cylinders to count when I was young by getting dirt into the exhaust and then just restarting the engine. After the next few runs all compression was lost. Due to the open exhaust and two of them, Cox engines are really easy to get dirt into. Just a thought...

AJC

< Message edited by ajcoholic -- 3/3/2004 6:27:08 PM >


_____________________________

Andrew J. Coholic
Engine reviewer for FLY RC Magazine - andrewc@flyrc.com

(in reply to DesignMan)
       Post #: 3

RE: no compression - 3/4/2004 1:23:29 AM   
Dr.Weasel



Posts: 184
Joined: 2/15/2004
From: layton, UT, USA
Status: offline 		First off this engine is so small that the glow plug is the head.

This engine is very similar to mine
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXB444&P=0

This is the glow plug i'm talking about
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXB450&P=0

Also it didn't come with a gasket in between the glowplug and the cylinder.

The air and fuel mixture isn't bypassing the piston it is leaking in between
the cylinder and the glowplug. I tightened the plug down as hard as i could
and it still leaked. I also check both the threads on the cylinder and the glowplug
and they were fine. So i dont know is there supposed to be some filler or gasket
i'm supposed to use? It was working fine then about a day ago it wouldn't start so i
took the plug off to check it and the batteries. They were fine so i put it back on
and thats when i lost compression ( i have taken the plug off many times before and
never lost compression until now).

Please help me
The Doc.

(in reply to ajcoholic)
       Post #: 4

RE: no compression - 3/4/2004 1:43:53 AM   
Jim Thomerson



Posts: 2857
Joined: 10/9/2002
From: Austin, TX, USA
Status: offline 		There is supposed to be a thin copper gasket between the glow plug and head. I suspect the last time you took the head off the gasket got lost. It is not going to work without it. Email me your snailmail address and I'll send you a couple. You shouldn't have to take the head off to see if the plug is glowing. You should be able to look into the exhaust port and see a red glow. If not, you need a better charged battery, or a new glow plug. In bright sun use your hand or something to make some shade.

Jim

(in reply to Dr.Weasel)
       Post #: 5

RE: no compression - 3/4/2004 2:32:34 AM   
ajcoholic



Posts: 4045
Joined: 6/22/2002
From: Kirkland Lake, ON, CANADA
Status: offline 		I agree with JIm, the gasket probably stuck to the lower edge of the glowhead and then fell off.

Thats an easy fix once you get a few spares...

AJC


_____________________________

Andrew J. Coholic
Engine reviewer for FLY RC Magazine - andrewc@flyrc.com

(in reply to Jim Thomerson)
       Post #: 6

RE: no compression - 3/4/2004 5:21:16 AM   
Dr.Weasel



Posts: 184
Joined: 2/15/2004
From: layton, UT, USA
Status: offline 		Are you sure there is supposed to be a gasket because i'm positive mine didn't have one? Also tonight i took the plug off and inspected it then put it back on and i had compression again. Which is weird because i have tried this a couple times and it hasnt done anything until now.( got it started) but if you still have those gaskets i will try them out or if you know a website i can get them at i would like to know.

Thanks
The Doc.

(in reply to ajcoholic)
       Post #: 7

RE: no compression - 3/4/2004 11:18:41 AM   
Clean



Posts: 991
Joined: 4/19/2002
From: Parkville, MO, USA
Status: offline 		Absolutely, positivily, without a doubt, there is supposed to be AT LEAST ONE gasket in there, usually more. You control the compression of the engine with these as well as provide the sealing surface witht he gaskets.

Here is a source for gaskets from Norvel, same thing but call the order in and verify that they are for the 1/2A engines, they have 15's, 25's and 40's as well. Get several packets of them, they are cheap and get lost easily.

Cox QC is not quite what it used to be, and it was pretty shoddy in the past! Now that the only people that care don't work there anymore it's amazing that things even run.

_____________________________

From Somewhere near Parkville, Mo.
William Crane (aka Mr Clean) Rever Brother #168 Time Man of the Year

(in reply to Dr.Weasel)
       Post #: 8

RE: no compression - 3/5/2004 10:17:03 AM   
gcb



Posts: 2463
Joined: 10/24/2002
From: Port Ewen, NY, USA
Status: offline 		Doc,
If you have a spare glow plug, there should be a new copper gasket with it.

George

(in reply to Clean)
       Post #: 9

RE: no compression - 3/5/2004 3:15:35 PM   
Dr.Weasel



Posts: 184
Joined: 2/15/2004
From: layton, UT, USA
Status: offline 		$9.00 for a new glow plug!!!!! Do you think i'm rich or something Just kiddn, do know where i can just get the gaskets or are those norvel ones the only ones.

(in reply to gcb)
       Post #: 10

RE: no compression - 3/5/2004 3:38:23 PM   
gcb



Posts: 2463
Joined: 10/24/2002
From: Port Ewen, NY, USA
Status: offline 		The easiest way to get the gaskets is to take Jim up on his offer. The Norvel plug, as well as the gasket, will fit your engine and are cheaper. It may be easier to get the Cox glow plug locally though.
Keep any old gaskets you have. Some day you may want to add extra ones to "shim" the head for a particular application.

George

(in reply to Dr.Weasel)
       Post #: 11

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